Biology Unit 1 Part 1

1. Variation of metabolic rates
   1. Exercise
      1. Muscles contract more to move limbs so they need more energy
         1. Cells need to respire more to release more energy from glucose so you eat more
            1. Exercise increase the amount of energy expend by the body , so the metabolic rate is higher
2. Proportion of muscle to fat
   1. Fat cells store fat and they are inactive - low rate of respiration to ensure they don't lose their fat
   2. Muscles ells are active - high rate of respiration to ensure they don't lose their stored fat
   3. More muscles and less fat = high metabolic rate
   4. More fat and less muscle = low metabolic rate ( need to eat more food to supply energy for muscle cells
3. Inherited factors
   1. Tall people (higher metabolic rate) - lose more heat from body surface
   2. Overweight people (higher metabolic rate) - larger bodies need more energy to move
   3. Underactive thyroid gland - lower metabolic rate

1. Fats for energy
   1. Proteins build cells and reaper tissues
      1. Water (cells contain about 70% of it) is lost in sweat and urine etc.
         1. Fibre prevents constipation
            1. Mineral and ions - small amounts keep the body healthy

1. Can lead to deficiency disease
   1. Lack of vitamin D - rickets ( soft bendy bones , curved spine , enlarged skull)

1. Energy of the content of the food you eat is less than the energy you lose
   1. Don't eat enough or exercise to much
      1. Thin girls - irregular periods

1. If people too much
   1. Very overweight = obese (can cause type 2 diabetes)
      1. Inherited factors can also affect cholesterol levels

1. Helps strengthen cell membranes , and used to make sex hormones and vitamin D
   1. To much can increase the risk of heart disease
      1. Comes directly from meat , prawns and eggs
         1. Liver makes it from saturated fats in butter , chocolate and fatty meat
            1. Liver can make too much - take satins to reduce levels , taken in the evening as the body makes it during the night and it inhibits an enzyme involved in making cholesterol

1. Specific antibiotics target specific bacteria
   1. Cannot be used to kill viruses
      1. Drugs called antivirals stop your cells a making copies of the viruses
2. They stop bacteria from making cell walls or protein and viruses don't do this

1. MRSA
   1. Bacteria is resistant to methicillin (very strong antibiotic)
      1. Caused many deaths
         1. Lives in the skin but if it gets into a wound it causes harm
            1. Easily killed with antiseptics and disinfectants
2. 1. Bacteria infect you
   1. 2. One or two may have chance mutations and aren't killed by the medicine
      1. 3. New strain of bacteria that is resistant to antibiotics have developed

Annotations:

• Skin , stomach acid , tears , blood clotting and mucus in the airways 

1. Phagocytes - engulf (ingest) pathogens
2. Lymphocytes - produces antibodies or antitoxins
   1. Antibodies are proteins
      1. Each pathogen has particular antigens (proteins) wit ha specific shape on its surface
         1. Each type of antibody also has a particular shape which can lock onto the antigen
            1. Immune system makes the right antibodies
               1. Once the pathogen is coated with antibodies , white blood cells can ingest and kill the pathogen
                  1. Once recovered you are immune as your body knows how to make the right antibodies

1. Reduces the spread of infection
2. Flu virus - Mutates often so body doesn't recognise antigens (epidemic and pandemic)
3. 1. Small amount of dead or inactive pathogen is introduced to the body by an injection - still have antigens on surface
   1. 2. White blood cells respond by making antibodies
      1. 3. If live pathogens enter the body the white blood cells can quickly make the correct antibodies
         1. 4. Destroying the pathogens before you get ill

1. Not all pathogens
   1. Have millions on our skin or in our gut
      1. If they get into our blood or cells they can make us very ill
         1. Reproduce rapidly in our warm bodies
            1. Produce toxins that make us ill and can cause death

1. All pathogens
   1. Insert themselves into a host and hijack the cells parts to make copies of the virus
      1. New virus particles then burst out of cells an infect other cells - chain reaction
         1. Viruses damage and destroy cells
            1. Much smaller than bacteria
               1. Not made of cells and cannot carry out any life process so they are thought to not be alive

1. Have nucleus , cell membrane and cytoplasm
   1. Information passes from them as electrical impulses along nerve cells called neurone to the brain
      1. Brain then co-ordinates response
      2. Adaptations of neurones
         1. Long
         2. Insulating sheath - prevents impulses from leaking
         3. Branched ends - communicate with other neurones

1. 2. Pain receptors in the skin are stimulated
   1. 3. A nerve impulse (electrical) travels along the sensory neurone to the relay neurone
      1. 4. Then the impulse passes through a synapse to the brain
         1. 5. The impulse travels along the motor neurone
            1. 6. The nerve impulse then travels to effector
               1. 7. The muscles contract pulling the finger away (the response)
         2. Chemical reaction by diffusion

1. One that acts is quickly when the kidneys regulate water content of blood

1. Are produced (secreted) from glands into the bloodstream
   1. Travel in the blood to target organs

1. From skin in sweat
2. Lungs by breathing out
3. Kidneys in urine

1. From drinks and food containing water
2. Respiration of digested food
3. Kidneys help to regulate levels
4. One hormone helps the kidney to only pass out water when you have too much

1. Pills contain oestrogen and progesterone to prevent FSH from maturing the egg

1. IVF - test tube baby
   1. Benefits
      1. Infertile couples can have children
         1. Embryos can be screened for genetic diseases
            1. Choose when to have kids
               1. Wait until they can afford a family
                  1. Limit family size or they might not want children
   2. Problems
      1. Religious - playing God
         1. Embryos made cannot develop
            1. Should adopt instead
               1. Expensive
                  1. Side-effects (weight gain , mood swings)
   3. Inject mother with FSH and LH which causes ovaries to make more eggs than usual
      1. Eggs collected from mother and fertilised by fathers sperm
         1. When eggs developed into embers , two are chosen and inserted into the mothers womb

1. FSH causes eggs in ovaries to mature and stimulates ovaries to make oestrogen
   1. Oestrogen stimulates the pituitary gland to LH
      1. LH triggers the release of an egg (ovulation) from the ovary
         1. Oestrogen prevents more FSH being secreted and repairs the uterus lining
            1. Progesterone maintains the uterus lining and works with oestrogen to prevent the secretion of FSH
               1. If the egg isn't fertilised the uterus lining passes out of the body
                  1. Lining stays so the baby can develop if the egg is fertilised

1. Weed killers - use too much hormones
2. Rooting powder - helps cuttings to make new roots
3. Fruit ripening - prevent fruit from dropping
4. Control of dormancy - stop seeds from germinating in winter

1. Response to gravity
   1. Shoots grow up - negatively
      1. Roots grow down - positively
         1. Auxins aid growth of cells
            1. Top grows faster than bottom
               1. Bend downwards

1. Plants grow towards the light this is called positive phototropic response
   1. Light shines on the shoot and the auxins move to the shaded side
      1. Cells on the shaded side grow faster and the plant bends towards the light

1. 2. If they pass these trials they are tested in humans in clinical trials
   1. 3. Low doses are given to volunteers
      1. 4. Volunteers are divided into two groups
         1. 5. Double blind trial - no one knows who has what drug , fair and results can't be biased
            1. 6. Two groups compared
               1. 7. If the drug makes a real difference and causes no harm it is licensed for use
                  1. 8. Side-effects mean drugs are recalled
         2. Control group are given a placebo or dummy pill
         3. Experiment group are given the real drugs

1. Cannabis
   1. Very good painkiller - multiple sclerosis
   2. Lead to mental health problems
   3. Addiction to harder drugs (heroin and cocaine)
   4. Increase risk of heart attacks and strokes
2. Performance enhancing - anabolic steroids
3. Withdrawal symptoms
4. Leads to harder drugs

1. Tobacco , caffein , alcohol
2. Nicotine - addictive and causes cancer
3. Alcohol - damages nervous system and alters behaviour